It is known to place inside containers and the like receptacles more or less filled with dry ice, i.e. solid carbonic acid or similar PCM, which during the transportation time through the influence of the ambient surrounding temperature is brought to evaporate or sublimate, a process which is difficult to regulate. This result in high dry ice costs and an unsatisfactory function since the temperature inside the container hardly can be controlled as closely as desired.
It is further known to arrange walls at transport boxes and the like provided with preferably closed spaces and fill said spaces with a phase change material (PCM) having a high melting temperature e.g. water. The boxes are before the loading thereof with goods placed in a space so cold that the phase change material is transformed into a solid state. During the transport, the heat necessary for the re-conversion will be collected from the ambient air passing through the box walls leaving the interior more or less unaffected. On long transports, some problems may occur in case the PCM is water or freezing mixtures, since rather large volumes would be necessary in order to keep the desired low temperature inside the transport box interior.
The reason why the first mentioned alternative, i.e. to utilize known phase change materials of very low evaporating temperature type such as dry ice, liquid CO2, liquid nitrogen or the like as a matter of fact, is used rather sparsely, depends on the cost and on the fact that the extremely low temperatures often affect the goods transported in a negative way.
A further drawback likewise important, is that in cases where the goods transported is not allowed to be colder than +/−0° C., the goods has to be insulated from the dry ice containing receptacle holding the evaporating dry ice, which results in a bad and lower utilization of the cold energy of the dry ice and increased handling costs.